As an alternative to ACPI, you can use xbindkeys to catch keypress events. For instance, you can catch the XF86AudioMicMute keypress and then run an appropriate amixer command to toggle microphone muting.

Legacy-BIOS

In order to turn off UEFI booting you will need to boot into your BIOS and change the boot mode to Legacy. Afterward, follow the Beginner's Guide for standard installation instructions.

UEFI

Note: This procedure reflects a single user's experience, and no attempt was made to experiment with different settings.

Download the official ISO or create your own using something like Archiso. Follow the instructions for creating a UEFI bootable USB from the ISO. Note that the default bootloader works fine so there's no need to replace it with an alternative like rEFInd. In the BIOS under Startup, set "UEFI/Legacy Boot" to UEFI only and turn off CSM support (this step might not be necessary, try skipping it first if you like).

Upon saving your changes and restarting, the UEFI boot options from the USB stick should come up and you can proceed to installing Arch.

It appears that the default partition table (and Windows installation) uses MBR. To use UEFI, you should reformat the disk as GPT (wiping the drive in the process). Follow the instructions for creating the EFI system partition. gdisk recommends a size of 300M. Follow the Beginner's Guide to see how to correctly generate (and then fix) the fstab entry for the ESP.

Booting using an efibootmgr entry is quite simple (and doesn't require any extra packages). Simply follow the instructions for creating the EFISTUB and adding the efibootmgr entry. The note about Lenovo Thinkpads truncating the UEFI options doesn't apply to the X1: the recommended efibootmgr entry works fine. The note about escaping the backslashes in the initrd path does apply, verify with efibootmgr -v that the boot entry doesn't have any missing characters.

Hardware

Almost everything works out of the box. Install synaptics and video-intel drivers.

Fingerprint Reader

fingerprint-gui from the AUR is already patched to work with the X1's newer fingerprint reader. To get the gui's dropdown to recognize your device, you'll have to add your user to the plugdev group:

# gpasswd -a <username> plugdev

It has been seen that the relevant udev rules do not get set properly. To do this, open /usr/lib/udev/rules.d/40-libbsapi.rules with your favorite text editor to add (or create with) the following lines:

Power management

ACPI

The only special keys that seems to work out of the box are the sleep, wifi, and keyboard backlight keys. All of the others (volume, brightness, etc.) need to be mapped using something like acpid. Here are the relevant acpi events

As an alternative to ACPI, you can use xbindkeys to catch keypress events. For instance, you can catch the XF86AudioMicMute keypress and then run an appropriate amixer command to toggle microphone muting.